Asymmetric fluorine and chlorine side-chain engineered quinoxaline-based D-A copolymer for both fullerene and nonfullerene polymer solar cells

In this paper, one conjugated polymer, with asymmetric side chains of alkoxy-substituted difluorobenzene and alkoxy-substituted monochlorobenzene based on quinoxaline (Qx) as the electron acceptor unit, and alkylthiothiophene benzodithiophene (BDTTS) as the electron donor unit, namely PBDTTS-2FClQx, was synthesized and employed as an electron donor polymer with a compatible dual-acceptor strategy to fabricate ternary organic solar cells (OSCs). As a consequence, the optimized ternary OSC (PBDTTS-2FClQx:Y6:PC71BM = 1 : 0.9 : 0.1) exhibited a significantly enhanced PCE of 13.59% with simultaneously increased fundamental parameters, showing about 9.5% improvement compared to the control binary PBDTTS-2FClQx:Y6 (12.41%). Moreover, the optimal ternary device showed much better stability. The excellent results demonstrate that this Qx type copolymer bearing asymmetric side-chains could be a promising donor material for constructing efficient and stable OSCs.